Vehicles include various components which degrade at different rates and have to be serviced at different times. In addition, the degradation rate of each component may be affected by multiple parameters, some of which are overlapping with other components while others are non-overlapping. For example, in hybrid electric vehicles, a system battery may degrade based on the rate of battery usage, the age of the battery, temperature conditions, the nature of the battery, etc. As another example, an air filter coupled to the engine intake may degrade based on the age of the filter, air quality, ambient weather conditions, etc.
Various approaches have been developed to assess the state of health of a vehicle component. One example approach for determining the state of health of an intake air filter using statistical analysis is shown by Verdegan et al. in U.S. Pat. No. 9,061,224. Therein an algorithm is used to calculate the remaining useful life of the filter, with constants used in the algorithm selected based on laboratory and historical performance of the filter. In addition, the constants are updated during filter usage based on filter performance, as determined based on a measured pressure drop across the filter. Another example approach is shown by Goldberg in U.S. Pat. No. 7,174,273. Therein, filter clogging is inferred based on an increase in differential pressure measurement relative to predicted differential pressure.
However the inventors herein have identified various issues with such approaches. As one example, the above approaches rely on statistical analyses that can be computationally intensive. Consequently, they may require extensive memory and processor resources to assess the health of the air filter. As another example, the availability of differential pressure measurements may be limited since not all engine systems include a differential pressure sensor around the air filter. In some engine systems, no pressure sensors may be available around the air filter. As still another example, the effects of different operating conditions on the pressure measurement may not be explicitly accounted, leading to unwanted bias in the assessments. As yet another example, an operator may not be able to comprehend how much time is left before the air filter needs to be replaced when the filter health is indicated in terms of a percentage degradation. The operator may replace the filter before the complete life of the filter has been used, resulting is the inefficient and uneconomical use of the filter. Alternatively, the operator may delay replacement of the filter, compromising vehicle operation. Further, the vehicle operator may not be able to timely modify their driving characteristics to avert filter degradation.
In one example, some of the above issues may be addressed by a method for a vehicle, comprising: indicating a degradation state of an engine intake air filter based on smaller than expected spread of airflow reading when throttle angle is above an upper threshold. In this way, the remaining useful life of a vehicle component, such as an air filter, may be more accurately predicted and the information may be conveyed to the vehicle operator in a more comprehensible manner.
As an example, during transient engine operating conditions, a controller may vary the position of an intake throttle and measure a corresponding change in manifold air flow (MAF), or manifold pressure (MAP), sensed downstream of the throttle. The controller may provide higher weightage to readings sensed at higher degrees of throttle opening (e.g., 55 degrees or more), due to the larger effect of filter “clogginess” on MAF (and MAP) at larger throttle angles. The controller may then perform a statistical analysis of the collected data including recursively estimating each of a mean value and a standard deviation value of MAF, calibrated with reference to throttle angle. The results may be compared to corresponding values for a clean air filter. The controller may then determine a filter health based on the calibrated mean and standard deviation values of MAF. In one example, as the mean value of MAF and/or the standard deviation of MAF, at higher throttle angles, drops relative to a threshold, a clogginess factor of the filter may be increased, and the state of health of the filter may be decreased. The state of health may also be updated based on ambient weather conditions that can cause a sudden clogging of the filter (e.g., presence of sudden dust storm or snow storm that can clog the filter). The sensed state of health may then be converted into an estimate of a remaining life of the filter, including a time and/or distance of vehicle travel remaining before the air filter needs to be changed or serviced. The conversion may be based on the sensed state of health of the filter and further based on vehicle drive statistics including a time and/or distance of travel already completed by the vehicle, as well as operator driving patterns and habits.
In this way, the remaining life of a vehicle component may be accurately predicted without relying on computationally intensive algorithms. By using data sensed on-board the vehicle, in association with vehicle driving statistics, the state of health of a component may be calculated more accurately. For example, the internal resistance and capacitance of a system battery may be better determined by accounting for temperature effects, as well as the effects of aggressive operator driving behavior. As another example, the degree of clogging of an air filter may be more accurately predicted based on a recursive estimation of mean and standard deviation of air flow values at large throttle openings. By assessing an air filter while relying on air flow or manifold pressure data sensed during vehicle transients, a larger portion of data collected over a vehicle drive cycle can be leveraged for filter prognostics. In addition, the need for actively holding the engine in a defined speed-load region, to complete a prognostic or diagnostic routine, is reduced. By converting the sensed state of health into an estimate of a remaining time or duration of vehicle operation before component servicing is required, a vehicle operator may be better notified of the condition of the component. As a result, timely component servicing may be ensured, improving vehicle performance. By predicting the remaining life of a vehicle component via a recursive estimation of statistical features, the remaining life of the component may be predicted with less computation intensity, without compromising on the accuracy of prediction. This enables a margin to be provided that better ensures healthy operation of the component for the estimated remaining life. The prognsotics feature may provide an early indication of the remaining life the component to help a customer plan for maintenance ahead of time and avoid component failure. In addition, the convenience of online estimation may be provided in an easy to implement package. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.